1. Field
The present invention relates to a wireless communication device, a wireless communication program storage medium, and a wireless communication method.
2. Description of the Related Art
In recent years, a protocol of a wireless communication system called 3G (third generation) is widely employed.
The 3G has some developmental stages. In addition to a cellular phone employing the original 3G, a cellular phone employing 3.5G with a further higher communication speed or a protocol called HSDPA has entered the field. Furthermore, Super 3G or 3.9, or a protocol called LTE (Long Term Evolution) is currently under review.
FIG. 1 is a schematic diagram of a wireless communication system employing the LTE protocol.
A terminal (UE; User Equipment) 10 wirelessly communicates with a base station (eNB; evolved Node B) 20 in accordance with the LTE protocol. The base stations (eNB) 20 are connected to an IP network 40 through an access gateway (aGW) 30 that intermediates a flow of data between the base stations (eNB) 20 and the IP network 40. Although only one aGW 30 is illustrated in FIG. 1, a large number of aGWs are connected to the IP network 40, and one or multiple eNBs exist under each aGW. Although only one UE 10 is illustrated in FIG. 1, a large number of UEs exist, and the UEs can intercommunicate through the eNB, the aGW, and the IP network 40.
FIG. 2 illustrates a protocol diagram of the LTE protocol.
The protocol in the wireless communication system of the 3G group is divided into multiple layers. Similarly, the LTE protocol is also divided into multiple layers.
A layer 1 is a layer called a physical layer, and the layer 1 is a portion that performs the actual communication.
A layer 2 located on the upper side of the layer 1 has three sublayers including a MAC (Medium Access Control) sublayer, an RLC (Radio Link Control) sublayer, and a PDCP (Packet Data Convergence Protocol).
A block of processing functions arranged in a layer or a sublayer is called an entity. PDCP entities and RLC entities exist by the number of logical channels used in accordance with each logical channel (LCH; Logical Channel) and transmit and receive a PDU (Protocol Data Unit). In case of the LTE protocol, a data concealment process and a data interface process with a further upper layer (not shown) are executed in a PDCP entity. In an RLC entity, a data conversion process is executed, and also, a retransmission process that requests a retransmission of insufficient data is executed.
A MAC entity integrates the PDUs transmitted from the RLC entities into one PDU and forwards the PDU to the layer 1. In the receiver side, the MAC entity divides the PDU transmitted from the layer 1 into PDUs of respective logical channels and transmits the divided PDUs to the RLC entities of corresponding logical channels.
FIG. 3 is a wireless communication system diagram in the LTE protocol.
The layer 1 is omitted, and only the layer 2 is covered herein. Furthermore, only one logical channel is illustrated herein.
When transmitting data from the eNB side to the UE side, the data transmitted from the upper layer is temporarily accumulated in a buffer 213a of a PDCP entity 213 on the eNB side. The data is subjected to processes such as a concealment process and handed over to an RLC entity 212. In the RLC entity 212, the data transmitted from the PDCP entity 213 is temporarily accumulated in a buffer 212a. The data is subjected to either a data conversion process or a retransmission process and then transmitted to a MAC entity 211. In the MAC entity 211 too, the data transmitted from the RLC entity 212 is temporarily accumulated in a buffer 211a. The data of multiple logical channels is integrated and transmitted to the UE side through the physical layer not shown.
In the UE side, the data received through the physical layer is temporarily accumulated in a buffer 121a of a MAC sublayer 121. The data is divided into pieces of data each of which is for each logical channel and transmitted to an RLC sublayer 122 of a corresponding logical channel. In the RLC sublayer 122, the piece of data transmitted from the MAC sublayer 121 is temporarily accumulated in a buffer 122a. The data is subjected to a data conversion process or a retransmission process and transmitted to the PDCP entity 123. In the PDCP entity 123, the data received from the RLC entity 122 is temporarily accumulated in a buffer 123a. The data is subjected to a concealment releasing process and the like and further transmitted to the upper layer of the UE side.
Data is similarly transmitted from the UE side to the eNB side. In the UE side, the data received from the upper side is temporarily accumulated in the buffer 123a of the PDCP entity 123 and then transmitted to the RLC entity 122. In the RLC entity 122, the data transmitted from the PDCP entity 123 is temporarily accumulated in a buffer 122b and then transmitted to the MAC entity 121. In the MAC entity 121 too, the transmitted data is temporarily accumulated in a buffer 121b and then transmitted to the eNB side through the physical layer.
In the eNB side, the data received through the physical layer is temporarily accumulated in a buffer 211b of the MAC entity 211 and then transmitted to the RLC entity 212. In the RLC entity 212, the received data is temporarily accumulated in a buffer 212b and then transmitted to the PDCP entity 213. In the PDCP entity 213, the data received from the RLC entity 212 is temporarily accumulated in a buffer 213b and then transmitted to the upper layer of the eNB side.
Japanese Patent Application Publication No. 2004-297381 discusses a technique that switches the wireless communication network of the data destination when the buffer of a router is about to overflow in a case where multiple wireless communication networks are connected through the router for data transmission.
FIG. 4 is a wireless communication system diagram for describing a problem.
FIG. 4 is only different from FIG. 3 in that an application 100 is added. Overlapping descriptions of the items described in FIG. 3 will be omitted.
The application 100 may be, for example, an application program downloaded through wireless communication and executed in the UE, or may be an application program executed in another device such as a personal computer (PC) or the like when the UE is further connected to such a device.
If the application 100 is an application with a low throughput, i.e., if the application 100 receives data at a low speed, the data transmitted from the eNB side is not quickly transmitted to the application 100. In this case, a large amount of data may be accumulated in the buffers 123a and 122a, and the data may overflow from the buffers 123a and 122a, causing missing of data.
As the communication speed between the eNB side and the UE side becomes faster, the application 100 that is developed without taking into account such a high communication speed may not be able to deal with the speed.